Chronic traffic noise stress accelerates brain impairment and cognitive decline in mice

Noise exposure-induced the cerebral alterations: From emerging evidence to antioxidant-mediated prevention and treatment

It's well acknowledged that noise exposure has become a major environmental risk factor of public health. The previous standpoint holds that the main harm of noise exposure is to cause hearing loss of human. However, in the past two decades a large number of studies have linked the noise exposure to various cerebral changes. In this review, we summarized that noise exposure led to cerebral changes through breaking the redox balance, inducing neuroinflammation and neuronal apoptosis and altering the neurotransmission in numerous brain areas, including cortex, thalamus, hippocampus, amygdala, striatum and cerebellum. Those cerebral changes finally result in a variety of disorders, such as tinnitus, anxiety, depression, cognitive impairment and motor dysfunction. Furthermore, we reviewed several antioxidants, such as resveratrol, vitamin C, curcumin, N-acetylcysteine and α-asarone, and highlighted their protective mechanisms against noise exposure, aiming to provide a promising strategy to prevent and treat noise exposure-induced diseases. Taken together, noise exposure induces various cerebral changes and further leads to disorders in the central nervous system, which can be ameliorated by the treatment with antioxidants.

CD36-mediated ROS/PI3K/AKT signaling pathway exacerbates cognitive impairment in APP/PS1 mice after noise exposure

There is an association between noise exposure and cognitive impairment, and noise may have a more severe impact on patients with Alzheimer's disease (AD) and mild cognitive impairment; however, the mechanisms need further investigation. This study used the classic AD animal model APP/PS1 mice to simulate the AD population, and C57BL/6J mice to simulate the normal population. We compared their cognitive abilities after noise exposure, analyzed changes in Cluster of Differentiation (CD) between the two types of mice using transcriptomics, identified the differential CD molecule: CD36 in APP/PS1 after noise exposure, and used its pharmacological inhibitor to intervene to explore the mechanism by which CD36 affects APP/PS1 cognitive abilities. Our study shows that noise exposure has a more severe impact on the cognitive abilities of APP/PS1 mice, and that the expression trends of differentiation cluster molecules differ significantly between C57BL/6J and APP/PS1 mice. Transcriptomic analysis showed that the expression of CD36 in the hippocampus of APP/PS1 mice increased by 2.45-fold after noise exposure (p < 0.001). Meanwhile, Western Blot results from the hippocampus and entorhinal cortex indicated that CD36 protein levels increased by approximately 1.5-fold (p < 0.001) and 1.3-fold (p < 0.05) respectively, after noise exposure in APP/PS1 mice. The changes in CD36 expression elevated oxidative stress levels in the hippocampus and entorhinal cortex, leading to a decrease in PI3K/AKT phosphorylation, which in turn increased M1-type microglia and A1-type astrocytes while reducing the numbers of M2-type microglia and A2-type astrocytes. This increased neuroinflammation in the hippocampus and entorhinal cortex, causing synaptic and neuronal damage in APP/PS1 mice, ultimately exacerbating cognitive impairment. These findings may provide new insights into the relationship between noise exposure and cognitive impairment, especially given the different expression trends of CD molecules in the two types of mice, which warrants further research.

The role of NLRP3 inflammasome-mediated neuroinflammation in chronic noise-induced impairment of learning and memory ability

BACKGROUND

Noise pollution pervades daily working and living environment, becoming a serious public health problem. In addition to causing auditory impairment, noise independently contributes to cognitive decline as a risk factor. Though neuroinflammation plays an important role in noise-induced cognitive deficits, the mechanisms underlying noise-induced neuroinflammation in the hippocampus are still poorly understood. Glial hyperactivation of the NLRP3 inflammasome contributes to various neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). However, whether the NLRP3 inflammasome plays a role in noise-induced cognitive impairment remains to be further investigated.

METHODS

Adult male Wistar rats were exposed to 100 dB white noise (4 h/day) for 30 days with or without injection of the NLRP3 inhibitor MCC950 (10 mg/kg/day). The Morris water maze (MWM) test and the open field test (OFT) were performed to evaluate learning and memory ability of rats. HE staining was used to explore hippocampal pathological changes, while immunohistochemical staining was employed to evaluate the number and morphology of microglia and astrocytes. The mRNA levels of the NLRP3 inflammasome in the hippocampus were examined by Real-time PCR. The protein levels of NLRP3 inflammasome, inflammatory cytokines, p-Tau-S396, and amyloid-β (Aβ) 42 in the hippocampus were examined by Western blot. Immunofluorescence was used to observe the distribution of NLRP3 in glial cells and neurons, and the assembly of the NLRP3 inflammasome.

RESULTS

We found that noise exposure induced learning and memory impairment in rats, mainly related to the activation of microglia and astrocytes in hippocampus region. Noise exposure increased the protein levels of p-Tau-S396, Aβ42, ionized calcium binding adapter molecule 1 (Iba-1), glial fibrillary acidic protein (GFAP), interleukin (IL)-1β, IL-18, and tumor necrosis factor-α (TNF-α) in hippocampus. Furthermore, the hippocampus of noise-exposed rats showed elevated protein levels of NLRP3, ASC and cleaved caspase-1. The co-labeled immunofluorescence levels of Iba-1 or GFAP with NLRP3 significantly increased in the dentate gyrus (DG) region of the hippocampus. NLRP3 inhibitor MCC950 intervention reversed chronic noise-induced activation of NLRP3 inflammasome, AD-like pathologies and impairment of learning and memory in rats.

CONCLUSIONS

The NLRP3 inflammasome-mediated neuroinflammation played an essential role in chronic noise-induced cognitive dysfunction. These results provide novel strategies for the prevention and treatment of cognitive deficits caused by chronic noise.

Experimental playback of urban noise does not affect cognitive performance in captive Australian magpies

Exposure of wildlife to anthropogenic noise is associated with disruptive effects. Research on this topic has focused on behavioural and physiological responses of animals to noise, with little work investigating links to cognitive function. Neurological processes that maintain cognitive performance can be impacted by stress and sleep disturbances. While sleep loss impairs cognitive performance in Australian magpies, it is unclear whether urban noise, which disrupts sleep, can impact cognition as well. To fill this gap, we explored how environmentally relevant urban noise affected the performance of wild-caught, city-living Australian magpies (Gymnorhina tibicen tyrannica) on a cognitive task battery including associative and reversal learning, inhibitory control, and spatial memory. Birds were housed and tested in a laboratory environment; sample sizes varied across tasks (n=7-9 birds). Tests were conducted over 4 weeks, during which all magpies were exposed to both an urban noise playback and a quiet control. Birds were presented with the entire test battery twice: following exposure to, and in the absence of, an anthropogenic noise playback; however, tests were always performed without noise (playback muted during testing). Magpies performed similarly in both treatments on all four tasks. We also found that prior experience with the associative learning task had a strong effect on performance, with birds performing better on their second round of trials. Like previous findings on Australian magpies tested on the same tasks in the wild under noisy conditions, we could not find any disruptive effects on cognitive performance in a controlled experimental laboratory setting.

Effect of postbiotic Lactiplantibacillus plantarum LRCC5314 supplemented in powdered milk on type 2 diabetes in mice

Type 2 diabetes (T2D) is a chronic multifactorial disease characterized by a combination of insulin resistance and impaired glucose regulation. The alleviative effects of probiotics on T2D have been widely studied. However, studies on the effects of postbiotics, known as inactivated probiotics, on dairy products are limited. This study aimed to evaluate the effectiveness of postbiotic Lactiplantibacillus plantarum LRCC5314 in milk powder (MP-LRCC5314) in a stress-induced T2D (stress-T2D) mouse model. Compared with probiotic MP-LRCC5314, postbiotic MP-LRCC5314 significantly influenced stress-T2D-related factors. The administration of heat-killed MP-LRCC5314 reduced corticosterone levels, increased short-chain fatty acid production by modulating gut microbiota, and regulated immune response, glucose metabolism, stress-T2D-related biomarkers in the brain, gut, and adipose tissues, as well as glucose and insulin sensitivity. In addition, heat-killed MP-LRCC5314 treatment led to a decrease in pro-inflammatory cytokine levels and an increase in anti-inflammatory cytokine levels. Overall, these findings suggest that adding postbiotic MP-LRCC5314 to milk powder could serve as a potential supplement for stress-T2D mitigation.

Long-term exposure to air pollution and road traffic noise and incidence of dementia in the Danish Nurse Cohort

INTRODUCTION

We examined the association of long-term exposure to air pollution and road traffic noise with dementia incidence in the Danish Nurse Cohort.

METHODS

Female nurses were followed for dementia incidence (hospital contact or medication prescription) from 1993/1999 to 2020. Air pollution and road traffic noise levels were estimated at nurses' residences, and their associations with dementia were examined using Cox regression models.

RESULTS

Of 25,233 nurses 1409 developed dementia. Particulate matter with a diameter of ≤2.5 µm (PM2.5) was associated with dementia incidence, after adjusting for lifestyle, socioeconomic status, and road traffic noise (hazard ratio [95% confidence interval] 1.35 [1.15-1.59] per interquartile range of 2.6 µg/m3). There was no association of PM2.5 with dementia in physically active nurses. Association with road traffic noise diminished after adjusting for PM₂.₅ (1.02 [0.93-1.11] per 7.6 dB).

DISCUSSION

Long-term exposure to air pollution increases risk of dementia, and physical activity may moderate this risk.

HIGHLIGHTS

Long-term exposure to air pollution was associated with increased risk of dementia among female nurses from the Danish Nurse Cohort. Association of air pollution with dementia was independent of road traffic noise. Association of road traffic noise with dementia diminished after adjusting for air pollution. Physical activity moderated adverse effects of air pollution on dementia.

Shrinking the footprint of the criminal legal system through policies informed by psychology and neuroscience

The footprint of the legal system in the United States is expansive. Applying psychological and neuroscience research to understand or predict individual criminal behavior is problematic. Nonetheless, psychology and neuroscience can contribute substantially to the betterment of the criminal legal system and the outcomes it produces. We argue that scientific findings should be applied to the legal system through systemwide policy changes. Specifically, we discuss how science can shape policies around pollution in prisons, the use of solitary confinement, and the law's conceptualization of insanity. Policies informed by psychology and neuroscience have the potential to affect meaningful-and much-needed-legal change.

Low-frequency noise impairs righting reflex behavior by disrupting central nervous system in the sea slug Onchidium reevesii

Anthropogenic noise has significantly increased due to human activities, posing a threat to the health and survival of marine organisms. However, current studies have often emphasized its effects on the physiological aspects of marine organisms, while ignored the relationship between the neuroendocrine system and behavior. This study aimed to evaluate the righting behavior and relevant physiological functions of the central nervous system (CNS) in sea slug (Onchidium reevesii) exposed to low-frequency noise and subsequent noise removal. The duration of the sea slugs' righting reflex increased with longer noise exposure time. The degree of neuronal cell damage and apoptosis were significantly increased and relevant gene expressions were affected (Glu, AChE, FMRFamide and CaMKII) (P < 0.05). After the removal of noise, the righting reflex speed gradually recovered, and the degree of neuronal cell damage, apoptosis and the expression levels of genes continued to decrease. Pearson correlation analysis showed that the righting time was positively correlated with CNS tissue and DNA damage, apoptosis rate, and negatively correlated with the expression levels of genes. Therefore, low-frequency noise exposure causes damage to the CNS of sea slugs, subsequently impairing their normal behavior. Sea slugs exhibited partial recovery within 384 h after removing noise. These findings provide valuable insights into the effects of low-frequency noise on the CNS and behavior of marine invertebrates.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Noise and mental health: evidence, mechanisms, and consequences

The recognition of noise exposure as a prominent environmental determinant of public health has grown substantially. While recent years have yielded a wealth of evidence linking environmental noise exposure primarily to cardiovascular ailments, our understanding of the detrimental effects of noise on the brain and mental health outcomes remains limited. Despite being a nascent research area, an increasing body of compelling research and conclusive findings confirms that exposure to noise, particularly from sources such as traffic, can potentially impact the central nervous system. These harms of noise increase the susceptibility to mental health conditions such as depression, anxiety, suicide, and behavioral problems in children and adolescents. From a mechanistic perspective, several investigations propose direct adverse phenotypic changes in brain tissue by noise (e.g. neuroinflammation, cerebral oxidative stress), in addition to feedback signaling by remote organ damage, dysregulated immune cells, and impaired circadian rhythms, which may collectively contribute to noise-dependent impairment of mental health. This concise review linking noise exposure to mental health outcomes seeks to fill research gaps by assessing current findings from studies involving both humans and animals.

Systemic health effects of noise exposure

Noise, any unwanted sound, is pervasive and impacts large populations worldwide. Investigators suggested that noise exposure not only induces auditory damage but also produces various organ system dysfunctions. Although previous reviews primarily focused on noise-induced cardiovascular and cerebral dysfunctions, this narrow focus has unintentionally led the research community to disregard the importance of other vital organs. Indeed, limited studies revealed that noise exposure impacts other organs including the liver, kidneys, pancreas, lung, and gastrointestinal tract. Therefore, the aim of this review was to examine the effects of noise on both the extensively studied organs, the brain and heart, but also determine noise impact on other vital organs. The goal was to illustrate a comprehensive understanding of the systemic effects of noise. These systemic effects may guide future clinical research and epidemiological endpoints, emphasizing the importance of considering noise exposure history in diagnosing various systemic diseases.

Stumbling Blocks in the Investigation of the Relationship Between Age-Related Hearing Loss and Cognitive Impairment

The relationship between age-related hearing loss (ARHL) and cognitive impairment (CI) remains intricate. However, there is no robust evidence from experimental or clinical studies to elucidate their relationship. The key unaddressed questions are (a) whether there is a causal effect of ARHL on CI and (b) whether efficacious treatment of ARHL (such as hearing-aid use) ameliorates CI and dementia-related behavioral symptoms. Because of several methodological and systematic flaws/challenges, rigorous verification has not been conducted. Addressing these stumbling blocks is essential to unraveling the relationship between ARHL and CI, which motivated us to undertake this review. Here, we discuss the methodological problems from the perspectives of potential confounding bias, assessments of CI and ARHL, hearing-aid use, functional-imaging studies, and animal models based on the latest information and our experiences. We also identify potential solutions for each problem from the viewpoints of clinical epidemiology. We believe that "objectivity," specifically the use of more objective behavioral assessments and new computerized technologies, may be the key to improving experimental designs for studying the relationship between ARHL and CI.

Relationship Between Work-Related Noise Exposure and Cognitive Impairment: A Cross-Sectional Study in China

Background

Noise exposure and the risk of cognitive impairment are currently major public health issues.

Objective

This study aimed to analyze the relationship between noise exposure and early impairment of cognitive function from the perspective of occupational epidemiology and to provide evidence for the long-term prevention and treatment of dementia in the context of aging.

Methods

This study was conducted in China between May and August 2021. The independent variables were the type of hazardous factors, duration of noise exposure, perceived noise intensity, and cumulative noise exposure (CNE). The dependent variable was cognitive function, which was measured using the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA). Multiple linear and logistic regression were used to analyze the relationship between noise exposure and cognitive function and to establish an effect curve.

Results

The detection rates of cognitive dysfunction using the MMSE and MoCA were 1.1% and 36.2%, respectively. The predicted MMSE and MoCA scores showed a downward trend within the CNE value ranging from 90-140 dB.time. Each unit increase in CNE decreased cognitive function scores by 0.025 (0.037, 0.013) and 0.020 (0.037, 0.003) points,respectively.

Conclusions

From the perspective of occupational epidemiology, these findings reveal a potential link between long-term noise exposure and early cognitive impairment.

Characterization of Anxiety-Like Behaviors and Neural Circuitry following Chronic Moderate Noise Exposure in Mice

BACKGROUND

Commonly encountered nontraumatic, moderate noise is increasingly implicated in anxiety; however, the neural substrates underlying this process remain unclear.

OBJECTIVES

We investigated the neural circuit mechanism through which chronic exposure to moderate-level noise causes anxiety-like behaviors.

METHODS

Mice were exposed to chronic, moderate white noise [85 decibel (dB) sound pressure level (SPL)], 4 h/d for 4 wk to induce anxiety-like behaviors, which were assessed by open field, elevated plus maze, light-dark box, and social interaction tests. Viral tracing, immunofluorescence confocal imaging, and brain slice patch-clamp recordings were used to characterize projections from auditory brain regions to the lateral amygdala. Neuronal activities were characterized by in vivo multielectrode and fiber photometry recordings in awake mice. Optogenetics and chemogenetics were used to manipulate specific neural circuitry.

RESULTS

Mice chronically (4 wk) exposed to moderate noise (85 dB SPL, 4 h/d) demonstrated greater neuronal activity in the lateral amygdala (LA), and the LA played a critical role in noise-induced anxiety-like behavior in these model mice. Viral tracing showed that the LA received monosynaptic projections from the medial geniculate body (MG) and auditory cortex (ACx). Optogenetic excitation of the MG → LA or ACx → LA circuits acutely evoked anxiety-like behaviors, whereas their chemogenetic inactivation abolished noise-induced anxiety-like behavior. Moreover, mice chronically exposed to moderate noise were more susceptible to acute stress, with more neuronal firing in the LA, even after noise withdrawal.

DISCUSSION

Mice exposed to 4 wk of moderate noise (85 dB SPL, 4 h/d) demonstrated behavioral and physiological differences compared to controls. The neural circuit mechanisms involved greater excitation from glutamatergic neurons of the MG and ACx to LA neurons under chronic, moderate noise exposure, which ultimately promoted anxiety-like behaviors. Our findings support the hypothesis that nontraumatic noise pollution is a potentially serious but unrecognized public health concern. https://doi.org/10.1289/EHP12532.

Effects of Different Auditory Environments on Behavior, Learning Ability, and Fearfulness in 4-Week-Old Laying Hen Chicks

Environmental enrichment can improve animal welfare. As a method of environmental enrichment, the effect of different auditory stimulations on the behavior response and welfare of laying hen chicks has yet to be investigated. Therefore, this study was aimed at exploring the impact of various auditory exposures on the behavior, learning ability, and fear response of 4-week-old laying hen chicks. A total of 600 1-day-old chicks were randomly assigned to five different groups: C (control group), LM (Mozart's String Quartets, 65 to 75 dB), LN (recorded ventilation fans and machinery, 65 to 75 dB), HN (recorded ventilation fans and machinery, 85 to 95 dB), and HM (Mozart's String Quartets, 85 to 95 dB). The experiment was conducted from day 1 until the end of the experiment on day 28. Groups LM and LN were exposed to music and noise stimulation ranging from 65 to 75 dB. Groups HN and HM, meanwhile, received noise and music stimulation ranging from 85 to 95 dB. The control group (C) did not receive any additional auditory stimuli. During the experimental period, continuous behavioral recordings were made of each group of chicks from day 22 to day 28. On day 21, the PAL (one-trial passive avoidance learning) task was conducted. On days 23 and 24, OF (open field) and TI (tonic immobility) tests were performed, and the levels of serum CORT (corticosterone) and DA (dopamine) were measured. The results indicated that exposure to music and noise at intensities ranging from 85 to 95 dB could reduce comforting, preening, PAL avoidance rate, the total number of steps and grid crossings of OF, and the concentration of DA in 4 WOA chicks (p < 0.05), increase the freezing times of OF (p < 0.05); 65 to 75 dB of noise stimulation could reduce preening and total number steps of OF in 4 WOA chicks (p < 0.05), increase the freezing times of OF (p < 0.05); and 65 to 75 dB of music exposure could reduce the concentration of CORT in 4 WOA chicks (p < 0.05). Therefore, 65 to 75 dB of music exposure could produce positive effects on chicks and showed relatively low CORT level, whereas 85 to 95 dB of music and noise exposure could reduce comforting and preening behavior, impair learning ability, and increase the fear responses of chicks.

The Impact of Persistent Noise Exposure under Inflammatory Conditions

The aim of this study was to investigate the impact of noise exposure in an intensive care unit (ICU) environment on the development of postoperative delirium in a mouse model that mimics the ICU environment. Additionally, we aimed to identify the underlying mechanisms contributing to delirium and provide evidence for reducing the risk of delirium. In this study, to mimic an ICU environment, lipopolysaccharide (LPS)-injected sepsis mouse models were exposed to a 75 dB noise condition. Furthermore, we assessed neurobehavioral function and observed the level of neuroinflammatory response and blood-brain barrier (BBB) integrity in the hippocampal region. The LPS-injected sepsis mouse model exposed to noise exhibited increased anxiety-like behavior and cognitive impairment. Moreover, severe neuroinflammation and BBB disruption were detected in the hippocampal region. This study provides insights suggesting that persistent noise exposure under systemic inflammatory conditions may cause cognitive dysfunction and anxiety- like behavior via the mediation of BBB disruption and neuroinflammation. As a result, we suggest that the detailed regulation of noise exposure may be required to prevent the development of postoperative delirium.

Occupational and Environmental Noise Exposure and Extra-Auditory Effects on Humans: A Systematic Literature Review

Noise is a common harmful factor in our work and the environment. Most studies have investigated the auditory effects of noise exposure; however, few studies have focused on the extra-auditory effects of exposure to occupational or environmental noise. This study aimed to systematically review published studies on the extra-auditory effects of noise exposure. We reviewed literature from PubMed and Google Scholar databases up to July 2022, using the Patient, Intervention, Comparison, and Outcome criteria and Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify studies that reported extra-auditory effects of occupational or environmental noise exposure. Studies were evaluated utilizing validated reporting tools (CONSORT, STROBE) appropriate to study design. A total of 263 articles were identified, of which 36 were finally selected and reviewed. Upon conducting a review of the articles, exposure to noise can elicit a variety of extra-auditory effects on humans. These effects include circulatory effects linked to higher risk of cardiovascular disease and decreased endothelial function, nervous system effects correlated with sleep disturbance, cognitive impairment, and mental health problems, immunological and endocrinal effects connected to increased physiological stress response and metabolic disorders, oncological and respiratory effects associated with an elevated risk of acoustic neuroma and respiratory disorders, gastrointestinal effects linked to an increased risk of gastric or duodenal ulcer, and obstetric effects connected to the risk of preterm birth. Our review suggests that there are numerous extra-auditory effects of noise exposure on human, and further investigations are needed to fully understand these effects.

Traffic noise inhibits inhibitory control in wild-caught songbirds

Anthropogenic noise is ubiquitous across environments and can have negative effects on animals, ranging from physiology to community structure. Recent work with captive-bred zebra finches demonstrated that traffic noise also affects cognitive performance. We examined whether these results extend to animals that have experienced noise in the wild. We collected black-capped chickadees from areas frequently exposed to road traffic noise and tested them on a detour reaching task, a commonly used measure of inhibitory control. Those chickadees exposed to traffic noise playback had much lower performance on the task than control birds, indicating that noise negatively impacts inhibitory control. These data corroborate previous findings in lab-reared zebra finches. Furthermore, these results suggest that prior experience with traffic noise is not sufficient for animals to habituate to noise and overcome its negative effects on cognitive performance. Instead, noise-induced cognitive effects might have broad impacts on animal species living in noise-polluted habitats.

Acoustic Stress Induces Opposite Proliferative/Transformative Effects in Hippocampal Glia

The hippocampus is a brain region crucially involved in regulating stress responses and highly sensitive to environmental changes, with elevated proliferative and adaptive activity of neurons and glial cells. Despite the prevalence of environmental noise as a stressor, its effects on hippocampal cytoarchitecture remain largely unknown. In this study, we aimed to investigate the impact of acoustic stress on hippocampal proliferation and glial cytoarchitecture in adult male rats, using environmental noise as a stress model. After 21 days of noise exposure, our results showed abnormal cellular proliferation in the hippocampus, with an inverse effect on the proliferation ratios of astrocytes and microglia. Both cell lineages also displayed atrophic morphologies with fewer processes and lower densities in the noise-stressed animals. Our findings suggest that, stress not only affects neurogenesis and neuronal death in the hippocampus, but also the proliferation ratio, cell density, and morphology of glial cells, potentially triggering an inflammatory-like response that compromises their homeostatic and repair functions.

Air pollution and traffic noise interact to affect cognitive health in older Mexican Americans

BACKGROUND

Both air pollution and noise exposures have separately been shown to affect cognitive impairment. Here, we examine how air pollution and noise exposures interact to influence the development of incident dementia or cognitive impairment without dementia (CIND).

METHODS

We used 1,612 Mexican American participants from the Sacramento Area Latino Study on Aging conducted from 1998 to 2007. Air pollution (nitrogen dioxides, particulate matter, ozone) and noise exposure levels were modeled with a land-use regression and via the SoundPLAN software package implemented with the Traffic Noise Model applied to the greater Sacramento area, respectively. Using Cox proportional hazard models, we estimated the hazard of incident dementia or CIND from air pollution exposure at the residence up to 5-years prior to diagnosis for the members of each risk set at event time. Further, we investigated whether noise exposure modified the association between air pollution exposure and dementia or CIND.

RESULTS

In total, 104 incident dementia and 159 incident dementia/CIND cases were identified during the 10 years of follow-up. For each ∼2 µg/m3 increase in time-varying 1- and 5-year average PM2.5 exposure, the hazard of dementia increased 33% (HR = 1.33, 95%CI: 1.00, 1.76). The hazard ratios for NO2-related dementia/CIND and PM2.5-related dementia were stronger in high-noise (≥65 dB) exposed than low-noise (<65 dB) exposed participants.

CONCLUSION

Our study indicates that PM2.5 and NO2 air pollution adversely affect cognition in elderly Mexican Americans. Our findings also suggest that air pollutants may interact with traffic-related noise exposure to affect cognitive function in vulnerable populations.

Tactile stimulation improves cognition, motor, and anxiety-like behaviors and attenuates the Alzheimer's disease pathology in adult APPNL-G-F/NL-G-F mice

Alzheimer's disease (AD) is one of the largest health crises in the world. There are limited pharmaceutical interventions to treat AD, however, and most of the treatment options are not for cure or prevention, but rather to slow down the progression of the disease. The aim of this study was to examine the effect of tactile stimulation (TS) on AD-like symptoms and pathology in APP^{NL-G-F/NL-G-F} mice, a mouse model of AD. The results show that TS reduces the AD-like symptoms on tests of cognition, motor, and anxiety-like behaviors and these improvements in behavior are associated with reduced AD pathology in APP mice. Thus, TS appears to be a promising noninvasive strategy for slowing the onset of dementia in aging animals.

The impact of stress and anesthesia on animal models of infectious disease

Stress and general anesthesia have an impact on the functional response of the organism due to the detrimental effects on cardiovascular, immunological, and metabolic function, which could limit the organism's response to an infectious event. Animal studies have formed an essential step in understanding and mitigating infectious diseases, as the complexities of physiology and immunity cannot yet be replicated in vivo. Using animals in research continues to come under increasing societal scrutiny, and it is therefore crucial that the welfare of animals used in disease research is optimized to meet both societal expectations and improve scientific outcomes. Everyday management and procedures in animal studies are known to cause stress, which can not only cause poorer welfare outcomes, but also introduces variables in disease studies. Whilst general anesthesia is necessary at times to reduce stress and enhance animal welfare in disease research, evidence of physiological and immunological disruption caused by general anesthesia is increasing. To better understand and quantify the effects of stress and anesthesia on disease study and welfare outcomes, utilizing the most appropriate animal monitoring strategies is imperative. This article aims to analyze recent scientific evidence about the impact of stress and anesthesia as uncontrolled variables, as well as reviewing monitoring strategies and technologies in animal models during infectious diseases.

Emotional responses of piglets under long-term exposure to negative and positive auditory stimuli

The stress caused by sound is inevitable. The stress caused by noise and the positive effects of music can affect the endocrine of animals and their welfare. In this study, a total of 72 hybrid piglets (Large White × Duroc × Min pig) were randomly divided into 3 groups, including music (Mozart K.448, 60-70 dB), noise (recorded mechanical noise, 80-85 dB), and control (natural background sound, <40 dB) groups. S-IgA (secretory immunoglobulin A), IL-6 (interleukin-6), IL-8 (interleukin-8), and positive emotion-related behaviors were used as indicators to discuss whether noise induced stress and inflammation in piglets or whether music could have positive effects. Six hours of auditory exposure were given daily (10:00-16:00), which lasted for 56 days. Behavioral responses of the piglets were observed, and the concentrations of salivary S-IgA and serum IL-6 and IL-8 were measured. The results showed that the concentration of S-IgA increased in the noise and control groups on the 57th day (P < 0.05); S-IgA concentration in the music group was unchanged after long-term music exposure. The concentrations of IL-6 and IL-8 showed that long-term noise exposure might lead to stress and inflammation in piglets. Tail-wagging and play behaviors of the piglets in the music group were significantly greater than those in the noise and control groups, which implied that long-term music exposure improved the emotional state of the piglets in a restricted and barren environment.

Sleep loss in male rats contributes more to weight gain during sleep disruption than stress assessed by corticosterone

Sleep disruption (SD) promotes stress which may mediate the effect of SD induced by noise on bodyweight gain and food intake. We determined if the change in bodyweight during SD caused by noise was driven by stress (assessed by corticosterone) and whether the effects of noise on SD, stress and bodyweight were specific to the method of SD or a consequence of SD per se. We isolated stress from SD due to noise by exposing rats to noise during the darkphase to test whether darkphase noise stimulated weight gain, stress and food intake. Male Sprague-Dawley rats slept undisturbed, were exposed to noise during both circadian phases (lightphase vs darkphase) and lightphase gentle handling. Bodyweight, food intake, physical activity, vigilance states, and plasma corticosterone were determined. Darkphase noise did not affect vigilance states. Unlike lightphase noise, darkphase noise and lightphase gentle handling did not stimulate weight gain or food intake. Only gentle handling significantly increased corticosterone levels. Noise during the lightphase increasesed weight gain and food intake by causing SD and these effects were not driven by stress as assessed by corticosterone. These results may have significant implications for developing translational models of insomnia-induced obesity in humans.

Acute deletion of the central MR/GR steroid receptor correlates with changes in LTP, auditory neural gain, and GC-A cGMP signaling

The complex mechanism by which stress can affect sensory processes such as hearing is still poorly understood. In a previous study, the mineralocorticoid (MR) and/or glucocorticoid receptor (GR) were deleted in frontal brain regions but not cochlear regions using a CaMKIIα-based tamoxifen-inducible Cre ^ERT2/loxP approach. These mice exhibit either a diminished (MR^TMXcKO) or disinhibited (GR^TMXcKO) auditory nerve activity. In the present study, we observed that mice differentially were (MR^TMXcKO) or were not (GR^TMXcKO) able to compensate for altered auditory nerve activity in the central auditory pathway. As previous findings demonstrated a link between central auditory compensation and memory-dependent adaptation processes, we analyzed hippocampal paired-pulse facilitation (PPF) and long-term potentiation (LTP). To determine which molecular mechanisms may impact differences in synaptic plasticity, we analyzed Arc/Arg3.1, known to control AMPA receptor trafficking, as well as regulators of tissue perfusion and energy consumption (NO-GC and GC-A). We observed that the changes in PPF of MR^TMXcKOs mirrored the changes in their auditory nerve activity, whereas changes in the LTP of MR^TMXcKOs and GR^TMXcKOs mirrored instead the changes in their central compensation capacity. Enhanced GR expression levels in MR^TMXcKOs suggest that MRs typically suppress GR expression. We observed that hippocampal LTP, GC-A mRNA expression levels, and ABR wave IV/I ratio were all enhanced in animals with elevated GR (MR^TMXcKOs) but were all lower or not mobilized in animals with impaired GR expression levels (GR^TMXcKOs and MRGR^TMXcKOs). This suggests that GC-A may link LTP and auditory neural gain through GR-dependent processes. In addition, enhanced NO-GC expression levels in MR, GR, and MRGR^TMXcKOs suggest that both receptors suppress NO-GC; on the other hand, elevated Arc/Arg3.1 levels in MR^TMXcKOs and MRGR^TMXcKOs but not GR^TMXcKOs suggest that MR suppresses Arc/Arg3.1 expression levels. Conclusively, MR through GR inhibition may define the threshold for hemodynamic responses for LTP and auditory neural gain associated with GC-A.

Research Progress on the Etiology and Pathogenesis of Alzheimer's Disease from the Perspective of Chronic Stress

Due to its extremely complex pathogenesis, no effective drugs to prevent, delay progression, or cure Alzheimer's disease (AD) exist at present. The main pathological features of AD are senile plaques composed of β-amyloid, neurofibrillary tangles formed by hyperphosphorylation of the tau protein, and degeneration or loss of neurons in the brain. Many risk factors associated with the onset of AD, including gene mutations, aging, traumatic brain injury, endocrine and cardiovascular diseases, education level, and obesity. Growing evidence points to chronic stress as one of the major risk factors for AD, as it can promote the onset and development of AD-related pathologies via a mechanism that is not well known. The use of murine stress models, including restraint, social isolation, noise, and unpredictable stress, has contributed to improving our understanding of the relationship between chronic stress and AD. This review summarizes the evidence derived from murine models on the pathological features associated with AD and the related molecular mechanisms induced by chronic stress. These results not only provide a retrospective interpretation for understanding the pathogenesis of AD, but also provide a window of opportunity for more effective preventive and identifying therapeutic strategies for stress-induced AD.

High-intensity interval and moderate-intensity continuous training ameliorate the deteriorating acute effect of noise stress on corticosterone and testosterone in rats

PURPOSE

Noise has become an integral part of human life. Noise stress affect various physiological indices. In the present study, the effects of acute noise stress on corticosterone and testosterone and testosterone to cortisol ratio (T/C) in male rats, trained with two types of high-intensity interval training (HIIT) and moderate-intensity continuous training (MCT) were evaluated.

METHODS

42 male Wistar rats were divided randomly into seven groups, including the control group (C), control time (CT), exposure to acute noise stress (S), HIIT, MCT, HIIT with noise stress (HIIT + S), and MCT with noise stress (MCT + S). Exercise groups performed eight weeks of exercise training. One session of stress was induced in stress groups following the intervention (exercise or rest) period. Serum levels of corticosterone and T/C were measured through blood samples, taken 48 hours following the last session of exercise in the four exercise groups without noise stress and time control. Immediately after noise stress, blood samples were taken in 3 stress groups.

RESULTS

Serum level of corticosterone in the MCT group was significantly higher than CT and HIIT groups (P = 0.001). Considering the effect of acute noise stress, corticosterone was significantly higher in HIIT + S and MCT + S, respectively, compared to the noise stress group (P < 0.001). Testosterone level of the noise stress group was significantly lower than CT group (P < 0.001). Testosterone level in the S group was significantly lower than other stress groups (MCT + S and HIIT + S) (P < 0.001). T/C in HIIT + S group was significantly higher compared to S and MCT + S groups (P < 0.001).

CONCLUSION

HIIT and MCT, by priority, ameliorated the deteriorating effect of noise stress on testosterone and T/C; and it appears that the intensity and mode of previous exercise training affect the hormonal response to noise stress.

Redox Regulatory Changes of Circadian Rhythm by the Environmental Risk Factors Traffic Noise and Air Pollution

Significance: Risk factors in the environment such as air pollution and traffic noise contribute to the development of chronic noncommunicable diseases. Recent Advances: Epidemiological data suggest that air pollution and traffic noise are associated with a higher risk for cardiovascular, metabolic, and mental disease, including hypertension, heart failure, myocardial infarction, diabetes, arrhythmia, stroke, neurodegeneration, depression, and anxiety disorders, mainly by activation of stress hormone signaling, inflammation, and oxidative stress. Critical Issues: We here provide an in-depth review on the impact of the environmental risk factors air pollution and traffic noise exposure (components of the external exposome) on cardiovascular health, with special emphasis on the role of environmentally triggered oxidative stress and dysregulation of the circadian clock. Also, a general introduction on the contribution of circadian rhythms to cardiovascular health and disease as well as a detailed mechanistic discussion of redox regulatory pathways of the circadian clock system is provided. Future Directions: Finally, we discuss the potential of preventive strategies or "chrono" therapy for cardioprotection. Antioxid. Redox Signal. 37, 679-703.

Transcriptomic and Behavioral Studies of Small Yellow Croaker (Larimichthyspolyactis) in Response to Noise Exposure

Noise has the potential to induce physiological stress in marine fishes, which may lead to all sorts of ecological consequences. In the current study, we used the RNA-sequencing (RNA-seq) method to sequence the whole transcriptome of the brain in small yellow croaker (Larimichthys polyactis). The animals were exposed to a mix of noises produced by different types of boat played back in a tank, then the brain tissues were collected after the fish had been exposed to a 120 dB noise for 0.5 h. In total, 762 differently expressed genes (DEGs) between the two groups were identified, including 157 up regulated and 605 down regulated genes in the noise exposure group compared with the control group. Gene ontology (GO) enrichment analysis indicated that the most up regulated gene categories included synaptic membranes, receptor-mediated endocytosis and the neurotransmitter secretion process. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways found that endocytosis, cell adhesion molecules and the extracellular matrix (ECM) receptor interaction pathway were over-represented. Specifically, ECM-related genes, including lamin2, lamin3, lamin4, coll1a2, coll5a1 and col4a5 were down regulated in the noise exposure group, implying the impaired composition of the ECM. In addition, the behavioral experiment revealed that L. polyactis exhibited avoidance behaviors to run away from the noise source at the beginning of the noise exposure period. At the end of the noise exposure period, L. polyactis kept motionless on the surface of the water and lost the ability to keep their balance. Taken together, our results indicate that exposure to noise stress contributes to neurological dysfunction in the brain and impaired locomotor ability in L. polyactis.

Stress Affects Central Compensation of Neural Responses to Cochlear Synaptopathy in a cGMP-Dependent Way

In light of the increasing evidence supporting a link between hearing loss and dementia, it is critical to gain a better understanding of the nature of this relationship. We have previously observed that following cochlear synaptopathy, the temporal auditory processing (e.g., auditory steady state responses, ASSRs), is sustained when reduced auditory input is centrally compensated. This central compensation process was linked to elevated hippocampal long-term potentiation (LTP). We further observed that, independently of age, central responsiveness to cochlear synaptopathy can differ, resulting in either a low or high capacity to compensate for the reduced auditory input. Lower central compensation resulted in poorer temporal auditory processing, reduced hippocampal LTP, and decreased recruitment of activity-dependent brain-derived neurotrophic factor (BDNF) expression in hippocampal regions (low compensators). Higher central compensation capacity resulted in better temporal auditory processing, higher LTP responses, and increased activity-dependent BDNF expression in hippocampal regions. Here, we aimed to identify modifying factors that are potentially responsible for these different central responses. Strikingly, a poorer central compensation capacity was linked to lower corticosterone levels in comparison to those of high compensators. High compensators responded to repeated placebo injections with elevated blood corticosterone levels, reduced auditory brainstem response (ABR) wave I amplitude, reduced inner hair cell (IHC) ribbon number, diminished temporal processing, reduced LTP responses, and decreased activity-dependent hippocampal BDNF expression. In contrast, the same stress exposure through injection did not elevate blood corticosterone levels in low compensators, nor did it reduce IHC ribbons, ABR wave I amplitude, ASSR, LTP, or BDNF expression as seen in high compensators. Interestingly, in high compensators, the stress-induced responses, such as a decline in ABR wave I amplitude, ASSR, LTP, and BDNF could be restored through the "memory-enhancing" drug phosphodiesterase 9A inhibitor (PDE9i). In contrast, the same treatment did not improve these aspects in low compensators. Thus, central compensation of age-dependent cochlear synaptopathy is a glucocorticoid and cyclic guanosine-monophosphate (cGMP)-dependent neuronal mechanism that fails upon a blunted stress response.

Cerebral consequences of environmental noise exposure

The importance of noise exposure as a major environmental determinant of public health is being increasingly recognized. While in recent years a large body evidence has emerged linking environmental noise exposure mainly to cardiovascular disease, much less is known concerning the adverse health effects of noise on the brain and associated neuropsychiatric outcomes. Despite being a relatively new area of investigation, indeed, mounting research and conclusive evidence demonstrate that exposure to noise, primarily from traffic sources, may affect the central nervous system and brain, thereby contributing to an increased risk of neuropsychiatric disorders such as stroke, dementia and cognitive decline, neurodevelopmental disorders, depression, and anxiety disorder. On a mechanistic level, a significant number of studies suggest the involvement of reactive oxygen species/oxidative stress and inflammatory pathways, among others, to fundamentally drive the adverse brain health effects of noise exposure. This in-depth review on the cerebral consequences of environmental noise exposure aims to contribute to the associated research needs by evaluating current findings from human and animal studies. From a public health perspective, these findings may also help to reinforce efforts promoting adequate mitigation strategies and preventive measures to lower the societal consequences of unhealthy environments.

Deletion of Wnt10a Is Implicated in Hippocampal Neurodegeneration in Mice

The hippocampus plays an important role in maintaining normal cognitive function and is closely associated with the neuropathogenesis of dementia. Wnt signaling is relevant to neuronal development and maturation, synaptic formation, and plasticity. The role of Wnt10a in hippocampus-associated cognition, however, is largely unclear. Here, we examined the morphological and functional alterations in the hippocampus of Wnt10a-knockout (Wnt10a-/-) mice. Neurobehavioral tests revealed that Wnt10a-/- mice exhibited spatial memory impairment and anxiety-like behavior. Immunostaining and Western blot findings showed that the protein expressions of β-catenin, brain-derived neurotrophic factor, and doublecortin were significantly decreased and that the number of activated microglia increased, accompanied by amyloid-β accumulation, synaptic dysfunction, and microglia-associated neuroinflammation in the hippocampi of Wnt10a-/- mice. Our findings revealed that the deletion of Wnt10a decreased neurogenesis, impaired synaptic function, and induced hippocampal neuroinflammation, eventually leading to hippocampal neurodegeneration and memory deficit, possibly through the β-catenin signaling pathway, providing a novel insight into preventive approaches for hippocampus-dependent cognitive impairment.

Chronic Noise Exposure and Risk of Dementia: A Systematic Review and Dose-Response Meta-Analysis

Objective

Evidence is scarce about the effect of noise exposure on the risk of dementia. We conducted a systematic review and dose-response meta-analysis, aiming to explore the association between noise exposure and the risk of dementia.

Methods

We searched PubMed, EMBASE and the Cochrane Library to collect studies on chronic noise exposure and the risk of dementia from database inception to September 18, 2021 without language limitations. Two authors independently screened the literature, extracted data and assessed the risk of bias of the included studies. A dose-response meta-analysis and subgroup analysis were then conducted to detect the association between noise exposure and the risk of dementia by using Stata 14.0 software. This study is registered on PROSPERO (CRD42021249243).

Results

A total of 11 studies were eligible for qualitative synthesis, and nine were eligible for quantitative data synthesis. All of them showed moderate to high quality scores in the assessment of risk of bias. We found a positive linear association between the noise increment and dementia risk (R2 = 0.58). When noise exposure increased 57 dB, the RR of dementia was 1.47 (95% CI: 1.21–1.78). From the outcome subgroup of AD, AD and dementia, VaD and NAD, we also found a positive association (R2 = 0.68, 0.68, 0.58, respectively). When noise exposure increased by 25 dB, the RRs were 1.18 (95% CI: 1.14–1.23), 1.19 (95% CI: 1.14–1.23) and 1.17 (95% CI: 1.06–1.30), respectively. We found a nonlinear association between the noise increment and dementia risk when only cohort studies were included (R2 = 0.58). When noise exposure increased by 25 dB, the RR of dementia was 1.16 (95% CI: 1.12–1.20). From the subgroup of AD, AD and dementia, VaD and NAD of cohort studies, the regression curve showed a nonlinear positive association (R2 = 0.74, 0.71, 0.43, respectively). When noise exposure increased by 25 dB, the RRs were 1.17 (95% CI: 1.12–1.21), 1.17 (95% CI: 1.12–1.22) and 1.13 (95% CI: 0.99–1.28), respectively.

Conclusion

Based on the current evidence, exposure to noise may be a specific risk factor for dementia. To better prevent dementia, more rigorously designed studies are needed to explore the etiological mechanism of noise and dementia.

Noise as a cause of neurodegenerative disorders: molecular and cellular mechanisms

Noise as an environmental stressor becomes of increasing importance in our industrialized world, and especially traffic noise from the environment represents a potential novel neurodegenerative risk factor, as well as for hearing loss. A significant number of studies have been suggested that the overproduction of reactive oxygen species (ROS) has a complex role in stimulation of pathologic events. Experimental studies upon molecular pathways of traffic noise exposure proposed that it increased the level of stress hormones and mediated the inflammatory and oxidative stress (OS) pathways resulting in endothelial and neuronal dysfunction. Studies have shown that neurons are especially sensitive to OS due to high polyunsaturated fatty acids content in membranes, high oxygen uptake, and weak antioxidant defense. However, OS induces the necrotic and apoptotic cell deaths in the cochlea. Chronic noise is one of the many overall reasons of obtained sensorineural hearing loss which destroys cognitive functions in human and animals, as well as suppresses neurogenesis in the hippocampus. Nevertheless, behavioral disorders caused by noise are mainly accompanied with oxidative stress, but the clear molecular mechanism of neurodegeneration due to disruption of the pro- and antioxidant systems is still not fully understood. This paper aims to highlight the down-stream pathophysiology of noise-induced mental disorders, including hearing loss, annoyance, anxiety, depression, memory loss, and Alzheimer's disease, describing the underlying mechanisms of induction of inflammation and oxidative stress.

Investigating audible and ultrasonic noise in modern animal facilities

Background: The environmental housing conditions of laboratory animals are important for both welfare and reliable, reproducible data. Guidelines currently exist for factors such as lighting cycles, temperature, humidity, and noise, however, for the latter the current guidelines may overlook important details. In the case of the most common laboratory species, the mouse, the range of frequencies they can hear is far higher than that of humans. The current guidelines briefly mention that ultrasonic (>20 kHz) frequencies can adversely affect mice, and that the acoustic environment should be checked, though no recommendations are provided relating to acceptable levels of ultrasonic noise. Methods: To investigate the ultrasonic environment in a large mouse breeding facility (the Mary Lyon Centre at MRC Harwell), we compared two systems, the Hottinger Bruel and Kjaer PULSE sound analyser, and an Avisoft Bioacoustics system. Potential noise sources were selected; we used the PULSE system to undertake real-time Fourier analysis of noise up to 100 kHz, and the Avisoft system to record noise up to 125 kHz for later analysis. The microphones from both systems were positioned consistently at the same distance from the source and environmental conditions were identical. In order to investigate our result further, a third system, the AudioMoth (Open Acoustic Devices), was also used for recording. We used DeepSqueak software for most of the recording analysis and, in some cases, we also undertook further spectral analysis using RX8 (iZotope, USA). Results: We found that both systems can detect a range of ultrasonic noise sources, and here discuss the benefits and limitations of each approach. Conclusions: We conclude that measuring the acoustic environment of animal facilities, including ultrasonic frequencies that may adversely affect the animals housed, will contribute to minimising disruption to animal welfare and perturbations in scientific research.

Prenatal stress dysregulates resting-state functional connectivity and sensory motifs

Prenatal stress (PS) can impact fetal brain structure and function and contribute to higher vulnerability to neurodevelopmental and neuropsychiatric disorders. To understand how PS alters evoked and spontaneous neocortical activity and intrinsic brain functional connectivity, mesoscale voltage imaging was performed in adult C57BL/6NJ mice that had been exposed to auditory stress on gestational days 12-16, the age at which neocortex is developing. PS mice had a four-fold higher basal corticosterone level and reduced amplitude of cortical sensory-evoked responses to visual, auditory, whisker, forelimb, and hindlimb stimuli. Relative to control animals, PS led to a general reduction of resting-state functional connectivity, as well as reduced inter-modular connectivity, enhanced intra-modular connectivity, and altered frequency of auditory and forelimb spontaneous sensory motifs. These resting-state changes resulted in a cortical connectivity pattern featuring disjoint but tight modules and a decline in network efficiency. The findings demonstrate that cortical connectivity is sensitive to PS and exposed offspring may be at risk for adult stress-related neuropsychiatric disorders.

Road traffic noise and cognitive function in older adults: a cross-sectional investigation of The Irish Longitudinal Study on Ageing

Background

The World Health Organization published updated Environmental Noise Guidelines in 2018. Included are recommended limit values for environmental noise exposure based on systematic reviews for a range of health outcomes, including cognitive impairment. There is emerging evidence in the literature that chronic exposure to road traffic noise may affect cognitive function in older adults, but this relationship is not well established. This study spatially linked nationally representative health microdata from The Irish Longitudinal Study on Ageing to building-level modelled noise data for two cities in the Republic of Ireland. This was used to investigate associations between exposure to road traffic noise and cognitive function in a sample of older adults, independent of a range of socio-demographic and behavioural characteristics, as well as exposure to air pollution.

Methods

We used the Predictor-LimA Advanced V2019.02 software package to estimate noise originating from road traffic for the cities of Dublin and Cork in Ireland according to the new common noise assessment methodology for the European Union (CNOSSOS-EU). Noise exposure values were calculated for each building and spatially linked with geo-coded TILDA microdata for 1706 individuals aged 54 and over in the two cities. Ordinary least squares linear regression models were estimated for eight standardised cognitive tests including noise exposure as an independent variable, with standard errors clustered at the household level. Models were adjusted for individual sociodemographic, behavioural and environmental characteristics.

Results

We find some evidence that road traffic noise exposure is negatively associated with executive function, as measured by the Animal Naming Test, among our sample of older adults. This association appears to be accounted for by exposure to air pollution when focusing on a sub-sample. We do not find evidence of an association between noise exposure and memory or processing speed.

Conclusions

Long term exposure to road traffic noise may be negatively associated with executive function among older adults.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-11853-y.

Prenatal and postnatal traffic pollution exposure, DNA methylation in Shank3 and MeCP2 promoter regions, H3K4me3 and H3K27me3 and sociability in rats' offspring

Background

Road traffic air pollution is linked with an increased risk of autistic spectrum disorder (ASD). The aim of this study is to assess the effect of exposure to prenatal or postnatal traffic-related air pollution combining concomitant noise pollution on ASD-related epigenetic and behavioral alternations on offspring.

Methods

A 2 × 2 factorial analysis experiment was designed. Wistar rats were exposed at different sites (L group: green space; H group: crossroads) and timings (E group: full gestation; P group: 21 days after birth) at the same time, and air pollutants of nitrogen dioxide (NO₂) and fine particles (PM_2.5) were meanwhile sampled. On postnatal day 25, brains from offspring of each group were extracted to determine the levels of DNA methylation in Shank3 (three parts: Shank3_01, Shank3_02, Shank3_03) and MeCP2 (two parts: MeCP2_01, MeCP2_02) promoter regions, H3K4me3 and H3K27me3 after three-chamber social test. Meanwhile, the Shank3 and MeCP2 levels were quantified.

Results

The concentrations of PM_2.5 (L: 58.33 µg/m³; H: 88.33 µg/m³, P < 0.05) and NO₂ (L: 52.76 µg/m³; H: 146.03 µg/m³, P < 0.01) as well as the intensity of noise pollution (L: 44.4 dB (A); H: 70.1 dB (A), P < 0.001) differed significantly from 18:00 to 19:00 between experimental sites. Traffic pollution exposure (P = 0.006) and neonatal exposure (P = 0.001) led to lower weight of male pups on PND25. Male rats under early-life exposure had increased levels of Shank3 (Shank3_02: timing P < 0.001; site P < 0.05, Shank3_03: timing P < 0.001) and MeCP2 (MeCP2_01: timing P < 0.001, MeCP2_02: timing P < 0.001) methylation and H3K4me3 (EL: 11.94 µg/mg; EH: 11.98; PL: 17.14; PH: 14.78, timing P < 0.05), and reduced levels of H3K27me3 (EL: 71.07 µg/mg; EH: 44.76; PL: 29.15; PH: 28.67, timing P < 0.001; site P < 0.05) in brain compared to those under prenatal exposure. There was, for female pups, a same pattern of Shank3 (Shank3_02: timing P < 0.001; site P < 0.05, Shank3_03: timing P < 0.001) and MeCP2 (MeCP2_01: timing P < 0.05, MeCP2_02: timing P < 0.001) methylation and H3K4me3 (EL: 11.27 µg/mg; EH: 11.55; PL: 16.11; PH: 15.44, timing P < 0.001), but the levels of H3K27me3 exhibited an inverse trend concerning exposure timing. Hypermethylation at the MeCP2 and Shank3 promoter was correlated with the less content of MeCP2 (female: EL: 32.23 ng/mg; EH: 29.58; PL: 25.01; PH: 23.03, timing P < 0.001; site P < 0.05; male: EL: 31.05 ng/mg; EH: 32.75; PL: 23.40; PH: 25.91, timing P < 0.001) and Shank3 (female: EL: 5.10 ng/mg; EH: 5.31; PL: 4.63; PH: 4.82, timing P < 0.001; male: EL: 5.40 ng/mg; EH: 5.48; PL: 4.82; PH: 4.87, timing P < 0.001). Rats with traffic pollution exposure showed aberrant sociability preference and social novelty, while those without it behaved normally.

Conclusions

Our findings suggest early life under environmental risks is a crucial window for epigenetic perturbations and then abnormalities in protein expression, and traffic pollution impairs behaviors either during pregnancy or after birth.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01170-x.

Relationship Between Chronic Noise Exposure, Cognitive Impairment, and Degenerative Dementia: Update on the Experimental and Epidemiological Evidence and Prospects for Further Research

Degenerative dementia, of which Alzheimer's disease is the most common form, is characterized by the gradual deterioration of cognitive function. The events that trigger and promote degenerative dementia are not clear, and treatment options are limited. Experimental and epidemiological studies have revealed chronic noise exposure (CNE) as a potential risk factor for cognitive impairment and degenerative dementia. Experimental studies have indicated that long-term exposure to noise might accelerate cognitive dysfunction, amyloid-β deposition, and tau hyperphosphorylation in different brain regions such as the hippocampus and cortex. Epidemiological studies are increasingly examining the possible association between external noise exposure and dementia. In this review, we sought to construct a comprehensive summary of the relationship between CNE, cognitive dysfunction, and degenerative dementia. We also present the limitations of existing evidence as a guide regarding important prospects for future research.

Effects of early noise exposure on hippocampal-dependent behaviors during adolescence in male rats: influence of different housing conditions

Central nervous system (CNS) development is a very complex process that can be altered by environmental stimuli such as noise, which can generate long-term auditory and/or extra-auditory impairments. We have previously reported that early noise exposure can induce hippocampus-related behavioral alterations in postnatal day (PND) 28 adolescent rats. Furthermore, we recently found biochemical modifications in the hippocampus (HC) of these animals that seemed to endure even in more mature animals (i.e. PND35) and that have not been studied along with behavioral correlates. Thus, the aim of this work was to reveal novel data about the effects of early noise exposure on hippocampal-dependent behaviors in more mature animals. Additionally, extended enriched environment (EE) housing was evaluated to determine its capacity to induce behavioral modifications, either by its neuroprotective ability or the greater stimulation that it generates. Male Wistar rats were exposed to different noise schemes at PND7 or PND15. Upon weaning, some animals were transferred to EE whereas others were kept in standard cages. At PND35, different hippocampal-dependent behavioral assessments were performed. Results showed noise-induced behavioral changes that differed according to the scheme and age of exposure used. In addition, housing in an EE was effective either in preventing some of these changes or in inducing the appearance of new behavioral modifications. These findings suggest that CNS development would be sensitive to the effects of different type of environmental stimuli such as noise or enriched housing, leading to maladaptive behavioral changes that last even until adolescence.

Effects of music stimulus on behavior response, cortisol level, and horizontal immunity of growing pigs

An enriched environment is widely used to improve domestic animals' welfare and promote their natural behaviors. Music can reduce abnormal behavior in humans, nonhuman primates, and rodents. However, little is known about the effects of music on pigs. This study aims to explore the effects of repeated music stimulation on the behavior, physiology, and immunity of growing pigs. A total of 72 hybrid piglets (Large White × Duroc × Minpig) were randomly divided into three groups, including music (Mozart K.448, 60 to 70 dB), noise (recorded mechanical noise, 80 to 85 dB), and control (natural background sound, <40 dB), and 6 h sound stimulation was given per day (1000 to 1600 hours) from 40 to 100 d of age. The behavioral activities of the pigs were observed during the music stimulation, and their serum cortisol, salivary cortisol, and serum immune indices were also measured. Compared with the control group, the music group and noise group increased activity but decreased lying of pigs (P < 0.05). A significant increase in tail-wagging, playing, and exploring behaviors of pigs was found in the music group (P < 0.05), and the noise significantly increased the aggressive behavior of the pigs (P < 0.05). Tail-wagging, playing, exploring, manipulating, and aggressive behaviors decreased over time. Short-term (8 d) music stimulus had a lower cortisol level than that of the noise and control groups (P < 0.05), whereas long-term (60 d) music stimulus increased immunoglobulin G (IgG), interleukin-2 (IL-2), and interferon-gamma (IFN-γ) levels (P < 0.05) and decreased interleukin-4 (IL-4) level (P < 0.05). Long-term noise stimulus significantly reduced the level of IgG (P < 0.05) but did not affect the level of IL-2, IL-4, and IFN-γ levels (P > 0.05). In conclusion, short-term music stimulus (8 d) reduced the stress response, whereas long-term music stimulus (60 d) enhanced the immune responses. In addition, the noise increased the aggressive behavior, and long-term noise reduced the immunity of the growing pigs.

Noise Damage Accelerates Auditory Aging and Tinnitus: A Canadian Population-Based Study

OBJECTIVE

Age-related hearing loss (ARHL) is the third most challenging disability in older adults. Noise is a known modifiable risk factor of ARHL, which can drive adverse health effects. Few large-scale studies, however, have shown how chronic noise exposure (CNE) impacts the progression of ARHL and tinnitus.

STUDY DESIGN

Retrospective large-scale study.

SETTING

Audiology clinical practice.

PATIENTS

In this study, 928 individuals aged 30-100 years without (n=497) or with the experience of CNE (n=431) were compared in their hearing assessments and tinnitus. In order to only investigate the impact of CNE on ARHL and tinnitus, people with other risk factors of hearing loss were excluded from the study.

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURES

Noise damage was associated with a greater ARHL per age decades (pure-tone average(PTA)0.5-4kHz alterations 19.6-70.8 dB vs. 8.0-63.2 dB, ≤0.001), an acceleration of developing a significant ARHL at least by two decades (PTA0.5-4kHz 33.4 dB at 50-59yr vs. 28.2 dB at 30-39yr, ≤0.001), and an increased loss of word recognition scores (total average 84.7% vs. 80.0%, ≤0.001). Significant noise-associated growth in the prevalence of tinnitus also was shown, including more than a triple prevalence for constant tinnitus (28.10% vs. 8.85%, ≤0.001) and near to a double prevalence for intermittent tinnitus (19.10% vs. 11.10%, ≤0.001). Noise also resulted in the elevation of the static compliance of the tympanic membrane throughout age (total average 0.61 vs. 0.85 mmho, ≤0.001).

CONCLUSIONS

Our findings emphasize the significant contribution of CNE in auditory aging and the precipitation of both ARHL and tinnitus.

Traffic-related Noise Exposure and Late-life Dementia and Cognitive Impairment in Mexican-Americans

BACKGROUND

Recently, it has been suggested that environmental exposures from traffic sources including noise may play a role in cognitive impairment in the elderly. The objective of the study was to investigate the association between local traffic-related noise pollution and incident dementia or cognitive impairment without dementia (CIND) during a 10-year follow-up period.

METHODS

1612 Mexican-American participants from the Sacramento Area Latino Study on Aging (SALSA) were followed every 12-15 months via home visits from 1998 to 2007. We used the SoundPLAN software package to estimate noise originating from local traffic with the input of Annual Average Daily Traffic (AADT) data from Metropolitan Planning Organizations (MPO) based on geocoded residential addresses at baseline (1998-1999). We estimated the risks of incident dementia or CIND from 24-hour and nighttime noise exposure using Cox proportional hazard models.

RESULTS

During the follow-up, we identified 159 incident dementia or CIND cases in total. Per 11.6 dB (interquartile range width) increase in 24-hour noise, the hazard of developing dementia or CIND increased (hazard ratio = 1.3 [1.0, 1.6]) during follow-up; estimates were slightly lower (hazard ratio = 1.2 [0.97, 1.6]) when adjusting for modeled local air pollution exposure from traffic sources. Overall, the risk of dementia/CIND was elevated when 24-hour and nighttime noise were higher than 75 and 65 dB respectively. See video Abstract: http://links.lww.com/EDE/B728.

CONCLUSIONS

In our study, traffic-related noise exposure was associated with increased risk of dementia or CIND in elderly Mexican-Americans. Future studies taking into account other noise sources and occupational noise exposure before retirement are needed.

Environmental noise degrades hippocampus-related learning and memory

The neural mechanisms underlying the impacts of noise on nonauditory function, particularly learning and memory, remain largely unknown. Here, we demonstrate that rats exposed postnatally (between postnatal days 9 and 56) to structured noise delivered at a sound pressure level of ∼65 dB displayed significantly degraded hippocampus-related learning and memory abilities. Noise exposure also suppressed the induction of hippocampal long-term potentiation (LTP). In parallel, the total or phosphorylated levels of certain LTP-related key signaling molecules in the synapses of the hippocampus were down-regulated. However, no significant changes in stress-related processes were found for the noise-exposed rats. These results in a rodent model indicate that even moderate-level noise with little effect on stress status can substantially impair hippocampus-related learning and memory by altering the plasticity of synaptic transmission. They support the importance of more thoroughly defining the unappreciated hazards of moderately loud noise in modern human environments.

Metabolic dysfunction modifies the influence of traffic-related air pollution and noise exposure on late-life dementia and cognitive impairment: A cohort study of older Mexican-Americans

Supplemental Digital Content is available in the text.

Cognitive impairment has been linked to traffic-related air pollution and noise exposure as well as to metabolic syndrome or some of its individual components. Here, we investigate whether the presence of metabolic dysfunction modifies associations between air pollution or noise exposures and incident dementia or cognitive impairment without dementia (CIND).